In the drilling and completion industry, the formation of boreholes for the purpose of production or injection of fluid is common The boreholes are used for exploration or extraction of natural resources such as hydrocarbons, oil, gas, water, and CO2 sequestration.
Surface-controlled, subsurface safety valves (“SCSSV's”) are typically used in production string arrangements to quickly close off the production borehole in the event of an emergency, such as a blowout. A usual form for an SCSSV is a flapper-type valve that includes a flapper member that is pivotally movable between open and closed positions within the borehole. The flapper member is actuated between the open and closed positions by a flow tube that is axially movable within the borehole.
After being placed into a borehole, mineral scale typically forms and builds up on all portions of the production tubing string that are exposed to borehole fluids. Scale and other buildup forming on and around the flow tube of the SCSSV can make it difficult to move the flow tube axially and thereby require more maintenance with respect to proper operation of the SCSSV. Prior devices for cleaning and removing or preventing scale buildups have focused on the interior surface of the borehole within the valve housing, as scale buildup in that location can inhibit the flow tube from moving axially and inhibit the valve from closing optimally. One such device includes wireline brushes, however this is costly as it necessitates stopping production operations to run the brush in and then conduct the cleaning. Another such device includes a wiper member that extends radially outwardly from the flow tube and into contact with an interior surface of the valve housing, which can counteract the effect of scale buildup and also operate to physically wipe away scale buildup. Another method for removing scale and debris buildup uses explosive charges. The use of explosives, however, carries with it risks of damage to valve components as well as the potential for damage to the production tubing string. Yet another method reduces the harmful effects of scale and debris build up by exercising the safety valve through operation of its components, to ensure any build up does not reach a point where the safety valve is no longer fully operational.
The art would be receptive to additional devices and methods for dealing with scale and debris buildup, particularly for areas not accessible using conventional cleaning techniques.